Still I am interested in how many companies actually make this stuff.
While companies may own the designs for their regulators, there are many manufacturing specific issues that can come up..
Regulators are not really high tech and theres quite a few companies making first stage casings in Europe, Asia, and the USA. Tooling up to produce a regulator body is well within the scope of most competant engineering operators, but, because the economies of scale are so small, only a few do it.
Its also quite common for a "brand" to have a cosmetically differant reg body externally, but internally the parts are identical to, and shared by other companies, again, economies of scale, and to keep costs down, many internal parts are identical between various brands. So often, its a situation of making a reg body "cosmetically around" the parts you have access to, and trust to deliver good performance.
Second stages bodies are just injection moulded items and these can be done anywhere the price is right, usually its cheapest in Asia, but, Italy has a very well respected injection moulding industry at competitive prices and many brands have their injection moulding done here, internally, again, many parts are shared.
Neoprene however, is very differant, this market is heavily dominated by Sheico, probably supplying more than 60% of the neoprene used in wetsuits and neoprene products world wide, irrespective of where its cut and stitched Sheico is by far and away the biggest player in this market.
They are also probably the biggest manufacturer of OEM wetsuits as well, and their cut and stitch factories make massive volumes of wetsuits for most of the big brands worldwide in Surfing, Scuba, Fishing,Boating etc.